[llvm] [DAG] Fold freeze(shuffle(x,y,m)) -> shuffle(freeze(x),freeze(y),m) (PR #90952)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

I've been able to simplify this a lot more than I expected - including adding isGuaranteedNotToBeUndefOrPoison handling

https://github.com/llvm/llvm-project/pull/90952